It has already become common that user's biological information which has excellent invariance and uniqueness is used for personal authentication using an Information device, and from among the biological information, fingerprint recognition has become the most attention-drawing and generalized authentication means due to the simple structure and comparatively excellent performance thereof. A common method for obtaining fingerprint information is an optical method using an optical refractor such as a prism.
As illustrated in FIG. 1, an optical fingerprint recognition device according to related arts includes a light source 1 for emitting light for fingerprint recognition, a prism 3 being in contact with a finger, a lens 4 for forming a fingerprint picture which is emitted from the prism 3, and an image sensor 5 for converting the fingerprint picture formed on the lens 4 into an electrical signal. The optical fingerprint recognition devices are classified into the scattering type devices and the absorption type devices according to the disposition structure of the prism 3 and the light source 1.
Light emitted from the light source 1 is incident into the prism 3, forms a fingerprint picture while being reflected, absorbed, or scattered at valleys and ridges of a fingerprint which contacts a fingerprint contact surface 3a of the prism 3, and is then emitted through an emitting surface 3b of the prism 3. The fingerprint picture emitted from the prism 3 is formed on the image sensor 5 through the lens 4 and thus a digital fingerprint picture is obtained.
Since the prism 3 has a triangular cross-sectional surface and changes a light path by a predetermined degrees or more, the fingerprint input device using the prism 3 cannot but have a larger volume than semiconductor type devices or the like even through any methods. Therefore, it is difficult to apply the optical fingerprint input device to a mobile device having a shape of a relatively thin panel.
As an alternative to this, Korean Patent Publication No. 10-2005-0090884 discloses a fingerprint input device which uses an optical refractor which does not have a triangular shape but have a plate shape so as to have a relatively small thickness. In the fingerprint input device, a light source is disposed on a side surface of an optical refractor to obtain a fingerprint picture by using light scattered in the optical refractor. The device uses a thin optical refractor, so that there is an effect of implementing a fingerprint input device with a small overall thickness.
However, referring to FIG. 13 and the description thereof or the like in the invention, it can be understood that the fingerprint input device disclosed in this invention is still implemented through a method in which the device is embedded in a mobile terminal (or a portable terminal). When a fingerprint input device is embedded in the terminal, the thickness of the terminal cannot but have a predetermined size or greater due to the fingerprint input device. Thus, such a related method has a problem in that the method not only cannot satisfy the tendency in which terminals have smaller thicknesses but also cannot be used in terminals which have already been produced and in use.